For years we have divided coral restoration into two primary modes; passive and active. These two modes were broadly defined in terms of where the human energy and resources were put in the hopes of bringing back ecosystem health and function. In passive restoration, the energy was put into stopping the threat and letting the ecosystem recover on its own accord. In active restoration, our energy and resources were put into assisting or facilitating the ecosystems recovery more directly. These terms always were a bit ambiguous, and poorly conveyed the nuance and complexity of the actions being performed by reef managers.

In a new paper by Hein et al., 2021, the authors discuss this issue, and propose the use of new terms to describe these two branches of restoration as they pertain to coral reefs. They introduce the term ‘proactive’ to replace passive, and ‘reactive’ to replace what was previously known as active restoration. These terms more accurately describe the actions being taken, and may make communicating the details of these projects more precise and relatable. We at Conservation Diver will be switching up our terminology in support of this, and here is why we think you should to.

Passive and Active coral restoration

For decades, the prevailing opinion and policy of reef managers was that protection is always preferred over restoration. That by stopping the threats to the ecosystem, the flora and fauna would rebound on its own, without further human interventions. From this came the term ‘passive restoration,’ essentially meaning that no time, energy, or resources were put into the ecosystem itself to return its health, diversity, and function. However, this term implies that nothing is being done, when in fact stopping the threat is anything except “passive.”

Tanote Bay Watershed
The reservoir above Tanote Bay, Kph Tao, constructed in 2006-2007 (Tanote Bay in in the upper right quadrant of the photo). Photo credit Ekapon Krobtong

For example, Tanote Bay on the island of Koh Tao, Thailand, was one of the more beautiful and vibrant reefs in the entire region. In 2006, the municipal government constructed a large water reservoir in the watershed above the bay to address the island’s unstable freshwater resources. However, this was done through massive deforestation, road cutting, and digging all the way to nearly to the highest peak in the watershed above the bay. By 2008, millions of tons of sand and clay had been washed into the bay, burying the reef under 1-2 meters of sediment. The reef was literally gone, and the water quality was extremely poor as more sediment loaded the area with each rain.

In 2008, we were working with the New Heaven Reef Conservation Program, the Save Koh Tao Community Group, and many community volunteers to ‘passively’ restore the bay by stopping the erosion and sedimentation. This required the planting of hundreds of thousands of Vetiver grass tillers and trees, constructing over a hundred check dams, and installing hundreds of erosion control logs and erosion control blankets. All of which took more than 3 years. In our minds, it was anything except passive, as the word is used in everyday language. However, since we were not working in the reef itself, that was how it was defined.

Tanote Restoration
Community members and volunteers help to restore the Tanote Bay Watershed

In the same way, the word ‘active restoration’ never really encompassed what mangers where doing or moving towards in their techniques and methods. As Hein et al. points out, in the past, restoration was thought of as the act of bringing the ecosystem back to its historical state. However, in the face of increased effects of climate change such as ocean warming and acidification, bringing ecosystems back to their historical state is not going to be possible. Instead, the focus must shift from maintaining historical species to maintaining the “key ecosystem processes, functions, and services through the next few decades of climate change.”

Proactive and Reactive Coral Restoration

The authors (Hein et al., 2021), propose the two new terms as a way to clarify the actions being done, and the intent behind them in the context of a rapidly changing planet. Proactive restoration would thus refer to any act or initiative aimed at “protecting and enabling recovery.” These proactive measures then go on to support the reactive measures “aimed at repairing ecosystem function and assisting the recovery of a degraded reef system, should it not be able to recover on its own.”

So, with this new, more accurate terminology, the things that we do to protect the ecosystem like erosion control, waste water treatment, and mooring buoy installations are viewed as proactive measures. Things which are done mostly in adjacent ecosystems that help to facilitate recovery within the target ecosystem. In some cases, like when there is still available structure and high larval supply, this can be all that is required to return the ecosystem services and function. And even in situations where those factors are not present, it is still the prerequisite for most successful reactive projects down the line.

Reactive projects in coral restoration would include coral gardening, artificial reefs, larval culturing and all the other projects reef managers implement as part of a successful holistic program. These are the actions taken to increase the health, abundance, and diversity of key species on the reef, or to improve their resilience and help them adapt to changing conditions. The authors of the report developed this graphic to help visualize the actions taken under each mode of coral restoration:

proactive reactive coral restoration
Methods or Proactive and Reactive Coral restoration, taken from Perspectives on the Use of Coral Reef Restoration as a Strategy to Support and Improve Reef Ecosystem Services, by Hein et al., 2021.

The coral restoration industry is still in its infancy, but is one that is becoming more urgently necessary as reefs around the world are in decline. While we work to solve the issues leading to climate change, we need to be proactive and reactive in out efforts to preserve ecosystem value and function. These new terms help to show not only the effort and planning that has to go into what was once called passive restoration, but also open up what was active restoration to include the work being done to build resilience and assist in the adaptation of corals through breeding programs. This is only one small point that this important report brought up, so stay tuned as we dive deeper into its recommendations and implications.